html and css, header image always the same size

I hope somebody can help me out. I'm trying to create a website with a big header image, which always has the same size, no matter how much you would zoom in or out. An example of what I want is this site:

http://ift.tt/1EY8URx

I would prefer to get this effect without using any javascript/jquery. Of course if needed, I can implement a javascript/jquery solution.

Thank you!